interface Speakable {
    name?:string,
    speak(): void,
    eat(): void,
}
interface Eatable {
    eat(): void
}
class Person implements Speakable,Eatable{
    speak(){
        console.log('Person说话');
    }
    eat(){}
}
class TangDuck implements Speakable{
    speak(){
        console.log('TangDuck说话');
    }
    eat(){}
}